Zolatron 64: starting point

Having decided to build a 6502 microcomputer, I was immediately successful in overcoming the first hurdle – and possibly one of the most critical stages in the whole project – by coming up with a name for it. It’s the Zolatron – or the Zolatron 64 to be precise, because it will have a total of 64K addressable memory.

However, that left me facing the next major obstacle – creating a logo. I’m glad to report that this milestone is behind us.

So, with all the difficult stuff out of the way I can now rest easy and fiddle around with the easy bits – designing the computer, building it and writing the software.

I’m undertaking this project in a bout of nostalgia for the early 1980s. If I were being genuinely true to the spirit of the age, of course, I would now start accepting your orders – and cheques – while promising a delivery date some time in the next six months (when we all really know it’ll be a year, or two, or maybe never).

There are probably laws against that kind of thing now, and I’m not going to be selling this as a product, so stop writing that cheque (or not, up to you).

Nonetheless, I do have to start thinking seriously about the design. For the Zolatron I haven’t got much further than deciding it’s going to be built around the 6502 and will have a couple of VIAs. The truth is, I’m a bit vague on how computers actually work. So I figured I’d start with a functioning one and work backwards.

The Apatco NCS 2056T is a kit that you build on a breadboard (supplied). It comes with a ROM containing some essential software (ie, a monitor program), a small LCD screen and input for a keyboard. Other than a suitable power supply, everything you need is in the kit. (Word of warning, though: it’s availability seems to be somewhat sporadic.)

You could probably put the parts together yourself much cheaper, although you then wouldn’t have the ROM software. And from my point of view the most valuable part of the whole kit is the documentation. This not only tells you how to wire it up, it goes through the principles behind stuff such as glue logic and address decoding.

I’ve got as far as reading the main manual and deciding that the address decoding for the Zolatron is going to be very different. The Apatco wastes most of the address space – which is fair enough in a design that’s intended for educational purposes only. Nonetheless, I will build the kit (and share my experiences) as per the instructions to start with and get the thing working before trying out my ideas. That way, when the computer stops working I’ll have a fighting chance of knowing where the problem lies.

This is my journey through the worlds of electronics, robotics and retro computing. I’m not an expert – I’m learning as I go, and this is my way of sharing what I’ve learned. Think of it as a geek's diary and lab notebook.